Page 80 - ITU Journal, Future and evolving technologies - Volume 1 (2020), Issue 1, Inaugural issue

ITU Journal on Future and Evolving Technologies, Volume 1 (2020), Issue 1

API callbacks into metamaterial hardware directives.
SDN app ecosystem Envisioned IoMMT apps
A notable trait of the Metamaterial Middleware is that
Device discovery
and registration Device access control Wireless Power Energy isolation and it is divided into two parts, in terms of system deploy-
app & permissions app Transfer security
ment [32]:
Device location discovery app Propagation optimization
Northbound Inteface IoMMT API 1. The metamaterial manufacturing stage component,
a complex, offline process requiring special meta-
SDN Controller IoMMT Middleware
DB material measurement and evaluation setups (dis-
Southbound Inteface - Unified IoT and IoMMT interface cussed in Section 5), and
2. The metamaterial operation stage component,
which operates in real time based on a codebook.
SDN Existing IoT, Networking and This codebook is a database populated once by
Controller Sensor infrastructure the manufacturing stage component and contains
IoMMT API
callback a comprehensive set of configurations for all meta-
Metamaterial unit
connected to the material API callbacks, supported by a given meta-
SDN Controller
material.
IoMMT API Contained and optimized propagation IoMMT API The operation stage component simply retrieves con-
callback callback
Interference-protected
area Environment figurations from the codebook and optionally combines
OR enabling
Avoided obstacle
OR software- them as needed, using an interleaving process described
Avoided untrusted defined
device in Section 5.
propagation
Transmitter Notably, other studies propose the use of online machine
Receiver
learning as a one-shot process, which can be more prac-
tical when response time is not a major concern [33].
However, in this work we propose the aforementioned
Fig. 6 – SDN schematic display of the system model and the separation in deployment, to ensure the fastest opera-
entire workflow abstraction.
tion possible overall, thus covering even the most de-
3. NETWORKED METAMATERIALS manding cases.
AND SDN WORKFLOWS It is noted that SDN is not a choice due to restric-
tions, but rather a choice due to compatibility. In the
Many metamaterials deployed within an environment software-defined metasurfaces presented in this paper, a
can be networked through their gateways. This means key point is the abstraction of physics via an API that
that they may become centrally monitored and config- allows networking logic to be reused in PWEs, without
ured via a server/access point in order to serve a partic- requiring a deep understanding of physics. SDN has
ular end objective. (among other things) already introduced this separa-
An example is given in Fig. 6, where a set of meta- tion of control logic from the underlying hardware and
materials is designed with the proper commands for its administrative peculiarities. Therefore, we propose
energy wave steering and focusing, in order to route an integration of PWE within SDN to better convey the
the energy waves exchanged between two wireless users, logical alignment of the two concepts.
thus avoiding obstacles or eavesdroppers. Other ap-
plications include wireless power transfer and wireless 4. APPLICATION PROGRAMMING
channel customization for an advanced quality of service INTERFACE FOR METAMATERI-
(QoS) [7, 13]. Such a space, where energy propagation ALS
becomes software defined via metamaterials is called a
programmable wireless environment (PWE) [8]. In the following, we consider a metamaterial in the form
As shown in [7], the PWE architecture is based of a rectangular tile. The term tile is used to refer to a
on the software-defined networking (SDN) principles. practical metamaterial product unit, which can be used
The PWE server is implemented within an SDN con- to cover large objects such as walls and ceilings in a
troller [31]; the southbound interface abstracts the meta- floorplan.
material hardware, treating metamaterial devices as A software process can be initiated for any metamaterial
networking equipment that can route energy waves (e.g. tile supporting a unique, one-to-one correspondence be-
similar to a router, albeit with a more extended and tween its available switch element configurations and a
unique parameterization). Thus, the metamaterial API large number of metamaterial functionalities. The meta-
constitutes a part of the northbound SDN interface, material tiles in this work incorporate tunable switch
atop of which the security, QoS and power transfer con- elements, which dictate the response of each individual
cepts can be implemented as SDN controller applica- cell, locally. In this way, providing an arrangement of
tions. On the other hand, the Metamaterial Middleware all the tile cells allows the tuning of the “concerted”
is part of the SDN middleware, translating metamaterial metamaterial response of the entire tile.

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